(1) Field of the Invention
This invention relates to a centrifugal separator suitable for collecting particles from liquid in which such particles are contained and for discharging the collected particles as concentrated liquid.
(2) Description of the Prior Art
Centrifugal separators are already known which include a mechanism which separates particles from liquid in which such particles are contained, collects the thus separated particles as concentrated liquid and automatically and continuously discharges the thus concentrated liquid therefrom to the outside. An exemplary one of such conventional centrifugal separators is shown in FIGS. 9a and 9b.
Referring to FIGS. 9a and 9b, the centrifugal separator shown is designed to separate and collect microorganisms and/or yeast from fermented liquid of such microorganisms and/or yeast and extract the microorganisms and/or yeast as concentrated liquid to the outside. The centrifugal separator thus has a collecting and extracting mechanism which includes a plurality of collecting chambers 4 provided in a circumferential direction of an inner peripheral wall of a rotor 3 composed of a drum cover 1 and a drum 2, a plurality of concentrated liquid deriving pipes 5 each having one end opened to a deepest portion of a collecting chamber 4 and extending downwardly in a contacting relationship with an inclined portion of the inner wall face of the drum 2 until the other end thereof is connected and opened to an outer peripheral side wall of a pairing chamber 31, and a plurality of pairing tube 32 extending obliquely downwardly from a base end portion of a stationary concentrated liquid extracting tube 6 and opened at the other ends thereof to the inside of the pairing chamber 31.
As apparently seen in FIG. 9b, each of the collecting chambers 4 is formed such that it has a substantially pyramid-shaped configuration with the inner peripheral wall of the drum 2 bent outwardly to provide inclined faces, and the deepest portion of each of the collecting chambers 4 is an outermost portion of the inner peripheral wall of the drum 2. A plurality of flow paths 33 are formed axially in and through a lower portion of the drum 2 from an outermost portion of the rotor 3.
With the centrifugal separator having such a construction as described above, centrifugally separated particles are moved along the inner peripheral wall of the rotor 3 and collected into the collecting chambers 4 and then introduced from the collecting chambers 4 into the concentrated liquid deriving pipes 5 and then into the pairing chamber 31. In the pairing chamber 31, the particles are turned together with the liquid and kinetic energy of them is converted into energy of pressure. By the energy of pressure, the concentrated liquid of the particles is flowed into the stationary pairing tube 32 and then forwarded to the outside by way of the concentrated liquid extracting tube 6. The flow paths 33 formed in the outermost portion of the rotor 3 have a function to intermediately wash the centrifugal separator during continuous running and are thus opened and closed by a hydraulic pressure or the like to permit particles accumulated in the collecting chambers 4 to be discharged to the outside to enable continuous running of the centrifugal separator for a long period of time.
In such a conventional centrifugal separator as described above, deposits of densely accumulated particles can be seen in the collecting chambers 4 during running of the centrifugal separator, but no deposit can be seen near exits of the concentrated liquid deriving pipes 5. In this instance, the particle concentration of concentrated liquid extracted from the concentrated liquid extracting pipe 6 exhibits a tendency that it decreases gradually as the running time passes. The phenomenon makes it impossible to successively extract particles smoothly and causes dispersion and/or elongation of the residence time of particles in a field of centrifugal force. Where such particles are weak like animal cells, there is the possibility that the survival rate of the particles may be deteriorated. Further, while concentrated liquid of such particles must be successively extracted under a low pressure by an enclosed system, it is considered that extraction under a pressure by the pairing chamber 31 is not preferable.